Influence of interphase mass transfer on the composition trajectories and crossing of boundaries in ternary azeotropic distillation

This paper examines the influence of mass transfer on the composition trajectories in multicomponent azeotropic distillation. Simulations were carried out for three different ternary systems: methanol-isopropanol-water,water-ethanol-acetone, and water-methanol-methylacetate. Two different models were used to calculate the composition trajectories in a tray column: an equilibrium (EQ) stage model and a rigorous nonequilibrium (NEQ) stage model based on the Maxwell-Stefan diffusion equations. The simulations show that the EQ and NEQ model trajectories could follow different composition paths and could end up in completely different corners of the composition space. Furthermore, in all the three case studies the NEQ model trajectory was found to cross the distillation boundary even when the boundary is a straight line. The study has implications for the development of improved separation strategies. (C) 2002 Elsevier Science B.V. All rights reserved.